Function; Control Function; Flow Direction; Vent Hole In The Actuator - GEM 550 Operating Instructions Manual

3 Product description
gland packing providing low-maintenance and reliable valve
spindle sealing even after a long service life. A wiper ring fit-
ted in front of the gland packing protects the seal against con-
tamination and damage.

3.3 Function

The product controls a flowing medium by being closed or
opened by a control medium.
The product has an optical position indicator as standard. The
optical position indicator indicates the OPEN and CLOSED po-
sitions.
Open position
Fig. 2: Optical position indicator

3.4 Control function

The following control functions are available:
Control function 1: Normally closed (NC)
Control function 2: Normally open (NO)
Control function 3: Double acting (DA)

3.5 Flow direction

The flow direction is indicated by an arrow on the valve body.
2/2-way body
under the seat
Angle valve body
under the seat
Over the seat
(code M)
GEMÜ 550
Closed position
2/2-way body
over the seat
Angle valve body
over the seat
Under the seat
(code G)
Under the seat (code G) is the preferred flow direction with in-
compressible liquid media to avoid water hammer
Over the seat (code M) only with control function - Normally
closed (NC)

3.6 Vent hole in the actuator

To vent the control medium, the pneumatic actuator has a
vent hole that is located on the side of the actuator housing
(control function normally closed). In certain areas of applica-
tion (e.g. the foodstuff industry), dirty water or cleaning media
could enter through this vent hole and penetrate the actuator,
thereby adversely affecting correct operation. A special vent
system with lip check valve is available for these applications,
which prevents such functional impairment.The vent hole at
the side is then closed.
Standard vent hole
6 / 46
Special vent system K-no.
6996
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